Are we alone in the universe? These Mars rocks could finally give us an answer.
The Perseverance rover has found some intriguing samples on the red planet. Here's what they might reveal about the origins of life in our universe—if we can get them back to Earth.
Across the Martian landscape, the view is breathtaking. Everything is quiet, except for a little robot patiently trundling up the sides of Jezero Crater. Perseverance, affectionately known as “Percy,” doesn’t have the ability to appreciate the reddish-orange hues of the desert landscape like a human can. But the rover has been exploring the red planet since 2021, and it’s been carefully amassing a rock collection that could change our understanding of Mars’ history, how it compares to our own planet, and how we came to be here.
Mars wasn’t always a desolate, dusty world. Scientists think that, at some point in the red planet’s history, it was temperate much like Earth is today. But around three or four billion years ago, Mars’s internal plumbing mysteriously shut off—and as a result, the red planet lost its protective magnetic field. Solar wind stripped the atmosphere over the next hundred million years or so, and the planet became the barren wasteland it is today.
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But billions of years ago, life may have formed within the water-rich environments that covered the red planet. And that’s what Perseverance is looking for—signs that ancient life may have once existed, and an understanding of what happened to Mars and why. That’s why the rover is collecting rocks and carefully preserving them in sample tubes that NASA hopes to collect within the next decade to bring back to Earth.
“Every single one of the samples on board the rover...has the potential to answer one or more of our most important questions about Mars,” says Meenakshi Wadhwa, a planetary scientist at Arizona State University, said. The mission is called Mars Sample Return, and Wadhwa serves as its principal scientist, helping to devise a plan to transport the rocks over a hundred million miles across our solar system.
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These Mars samples may record evidence of their age or “critical information about Mars’ ancient environment,” explains Ken Farley, deputy project scientist for Perseverance and a geochemist at Caltech. But more than anything, they have the power to tell us whether we’re alone in the universe. Here are some of the rocks that might help answer that fundamental question.
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The delta fan (samples 12-13)
Scientists picked Jezero Crater as Perseverance’s landing site in part because it may have been the site of an ancient river delta that flowed into a lake over three billion years ago. The water flowing through the delta deposited sediments into a fan shape, and NASA’s Perseverance rover began exploring the upper part of the fan in 2022.
“The front of the fan was really exciting to us because we were looking for ancient muddy lake-bottom deposits,” explains Briony Horgan, co-investigator and long-term planner for the Perseverance rover mission, as well as a planetary scientist at Purdue University. “You know, the kind of places where all the organic goo and junk would have washed into the lake and settled at the bottom.”
Initially the deposits looked more sandy rather than gooey. But upon further examination, scientists discovered that the sample does, in fact, have “muddy horizons” trapped with it. “We didn’t initially understand it because they’re actually preserved under these salty, sandy plates that we investigated a lot,” Horgan says. “But we found that once we drilled into it, [there was this] dark mud underneath.”
On Earth, this leftover, dried out mud would be an ideal place to preserve organics and fossilized ancient microbial life. “Think about like the gooiest mud you stepped in on the bottom of a lake, and all the signs of life that are in there,” she muses. “That's basically what we sampled.” But whether this Martian mud contains fossils is an open question.
The crater floor (sample 3)
The very first samples Perseverance took from the crater floor are crucial to understanding not only how Jezero Crater and Mars developed, but when.
“The samples we collected along the crater floor are very important for dating,” says Sandra Siljeström, an astrobiologist at RISE Research Institutes of Sweden who also works on the Mars Perseverance science team. “Because one important question is if there was life, when was the delta active and for how long? The dates we have in Jezero Crater, it’s like plus or minus half a billion years. It’s very inaccurate, and this is because we don’t actually have dateable rocks from a place where we know where they’re coming from.” In this case, context is everything; the fact that we know where samples came from and when they were taken is invaluable.
Because these crater floor samples came from igneous rocks forged in lava flows, they can help scientists understand the chemical composition of Mars’s interior, Wadhwa points out. That could help break down why Mars lost its magnetic field and became a barren world.
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The “bathtub ring” carbonate sample (sample 23)
Based on satellite images, Jezero appeared to have deposits of minerals called carbonates along the crater rim. “From orbit it almost looked like it could be a kind of bathtub ring,” says Horgan.
Scientists are still trying to figure out what exactly the carbonate ring represents—one hypothesis is that it’s an ancient beach deposit, though it’s hard to picture a stunning white sandy beach with blue water lapping at the shores on Mars. On Earth, these materials often form in the shallows of fresh water and alkaline lakes.
Carbonates are largely absent from Mars’s surface, but they’re abundant within Jezero’s ancient river delta. And this particular region, called the margin carbonate unit, was one Perseverance’s most highly anticipated destinations. The rover took three separate rock core samples from the area; two are sedimentary, while the other is silica-cemented carbonate.
“It’s not just interesting for life,” Horgan explains. “It’s also a great marker of the climate and environment on Mars.” The sedimentary samples could have come from rocks deposited by rivers and in lakes, Wadwa notes. “They could tell us about the range of environments that existed on ancient Mars.”
The Cheyava Falls sample (sample 25)
If you’ve heard of any Mars rock, it’s probably the Cheyava Falls sample. In July 2024, Perseverance grabbed a piece of a rock within Jezero Crater that was once exposed to flowing water. Images from the robot’s camera revealed “leopard spots”—fingerprints of chemical processes that microbial life could have used as a source of energy on Earth. The rock also contained strong evidence of organic molecules, which are the building blocks for life.
“This is a very fine-grained rock, and those are typically good at trapping and preserving biosignatures,” says Siljeström. “Biosignatures are things in a rock, which can be morphological or chemical information, that indicate life.”
This does not mean that Perseverance has found evidence of ancient life on Mars, however. To determine that, we’d need to return the samples to Earth.
The crater rim and future samples
Perseverance landed on the crater floor in February 2021, and it’s been making its way out of Jezero, along the delta fan and up the crater walls, ever since. In December 2024, the rover finally finished its 1,640-vertical-foot (500-vertical-meter) ascent and reached the top. In January 2025, the rover took its first sample from the crater rim, known as the Silver Mountain sample.
That means it’s likely older than the samples taken in Jezero Crater—it’s safe to say, in fact, that this sample is the oldest that Perseverance has collected. “That's important because it's believed that Mars was more habitable the longer you go back,” explains Siljeström. “The younger it becomes, the less water was probably available.”
As of this writing, Perseverance has collected and stored 21 tubes in its belly, including two “witness tubes” to help scientists filter out any Earth contaminants from the samples. The rover still has eight sample tubes and two witness tubes available for sample collection.
To confirm whether any of the rocks from Percy’s current or future stash are truly ancient or include fossilized microbial life, scientists would need to study all these samples in a lab.
“We can learn things from analyzing samples in laboratories that are just not possible from remote analyses by spacecraft,” says Wadhwa. From the camera resolution to radioisotope dating techniques to being able to hold a rock in your hand and tell whether it’s sedimentary or igneous, there are in-person lab techniques that simply cannot be replicated by a robot on Mars.
NASA is still trying to figure out mission logistics, and the earliest scientists might be able to study these rocks is the mid-2030s. But like the rocks that the Apollo missions returned from the moon, the Mars rocks would be priceless—scientifically speaking.
“Once you get those samples back, that means you have them for decades and decades, for generations to come,” concludes Horgan. “We’re still learning new things from the Apollo samples—we’re going on 60 years ago now. That's what we're really hoping to do is bring these samples back as a repository for future generations to keep learning about Mars.”
